Using respirometry for energy optimization in a nitrifying biological wastewater treatment system

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Courtesy of SURCIS, S.L.


Many wastewater treatment plants use more than 50% of their total energy budget in the aeration basin and, when nutrient removal is included in the activated sludge process, it is very common that the majority of oxygen uptake goes to the nitrification process. For that reason, in most wastewater treatment plants, energy optimization is focused on nitrification management. This information can be obtained in different ways, but perhaps the most direct way is based on the correct control of the minimum dissolved oxygen (DOmin) and sludge retention time (SRT) without impairment of process efficiency.

The present paper describes a relatively simple, fast procedure whereby the use of an advanced and high sensitivity respirometry system, both parameters are obtained throughout a novel method to accurately determine values of the half-saturation DO constant (KOA) and active nitrifier concentration (XA) from the results of a single respirometry test.

The procedure and methods here described do not aim to be a scientific document. On the contrary, one of its aims is to be accessible to any plant operator with access to a respirometer provided with necessary features to quickly obtain information about critical parameters on which the nitrification process can be calibrated so that it can be developed in the framework of its best energy optimization.

Keywords: respirometry, activated sludge process, dissolved oxygen, oxygen uptake rate, nitrfiers, nitrification, nitrification rate, nitrification capacity, half-saturation coefficient, minimum oxygen, sludge residence time, sludge age, energy optimization, respirometer, heterotrophic biomass, autotrophic biomass.

Customer comments

  1. By Kent Kuss on

    Emilio is correct! There is much to be learned and many dollars saved by getting an accurate look at the biomass activity level using respirometry. Whether it's a simple batch sample run in a 2 channel respirometer or a full panel of 8 to 16 samples, run with varying possible toxins, additives or food sources to see response time and acclamation or toxic effects, a true biological assessment of the biomass is key to every plant optimization plan. On-line respirometers for early warning of toxins and information that can allow a plant to optimize aeration can lead to significant savings of every plants energy dollars. ---------Respirometers for every budget.

  2. By David Laurier on

    Indeed, Emilio is correct. Visit our site at We have both on-line and lab respirometers, called Ra-TOX, Ra-COMBO.